Organic electroluminescence device and method for fabricating thereof

ABSTRACT

There are provided an organic EL device and a method of fabricating the same. An effective display area on which an anode electrode, an organic luminescence layer and a cathode electrode are formed is sealed by means of a metal can, a glass cap or an organic/inorganic material. A power source is applied to the anode and the cathode electrodes through a power transferring part extended from the effective display area to a non-effective display area. Accordingly, it is possible to reduce the oxidation of the cathode electrode of the organic EL device, thereby preventing the electrical contact characteristics of the cathode electrode from being deteriorated.

TECHNICAL FIELD

[0001] The present invention relates to an organic EL (ElectroLuminescence) device and a method of fabricating the same, and moreparticularly, to an organic EL device capable of reducing an oxidationof a cathode electrode, the cathode electrode applying a forward currentto the organic EL material.

BACKGROUND ART

[0002] In these days, an organic luminescence material has beendeveloped. The organic luminescence material has characteristics ofemitting a light when a forward current is applied to two electrodesinterposing the organic luminescence therebetween.

[0003] The organic luminescence material can emit a light having a redwavelength, a light having a green wavelength and a light having a bluewavelength according to the characteristics thereof.

[0004] Recently, an organic EL device has been developed by using thecharacteristics of the organic luminescence material. The organic ELdevice is lighter in weight and smaller in size than that of an LCD(Liquid Crystal Display) device.

[0005] In order to display an image in a full-color in the organic ELdisplay device, the organic EL requires an anode electrode, a cathodeelectrode and an organic luminescence layer having the organicluminescence material interposed between the anode and the cathodeelectrodes.

[0006] The anode electrode is disposed on a transparent substrate in amatrix configuration. The number of the anode electrode is three timesas many as a resolution of the organic EL device. The anode electrode isconnected with a thin film transistor disposed in the matrixconfiguration. The anode electrode is made of a transparent conductivematerial such as an ITO (Indium Tin Oxide) or an IZO (Indium ZincOxide).

[0007] The thin film transistor includes a gate electrode, a sourceelectrode, a drain electrode and a channel layer. The gate electrode ofthe thin film transistor is connected with a gate line, and the sourceelectrode of the thin film transistor is connected with a data line.

[0008]FIG. 1 is a cross-sectional view showing a conventional organic ELdevice.

[0009] Referring to FIG. 1, an anode electrode 1 is connected with thedrain electrode of the thin film transistor. The anode electrode 1supplies holes to the organic EL material.

[0010] The organic EL material includes a red organic EL material 4 foremitting a light having a red wavelength, a green organic EL material 6for emitting a light having a green wavelength and a blue organic ELmaterial 8 for emitting a light having a blue wavelength. The red, greenand blue EL materials 4, 6 and 8 are disposed on the anode electrode 1.

[0011] The cathode electrode 10 is disposed on the red, green and blueorganic EL materials 4, 6 and 8 so as to supply electrons coupled to theholes provided from the anode electrode 1. The cathode electrode 10 iscomprised of a pure aluminum or an aluminum alloy, and is disposed witha uniform thickness on a substrate to cover the anode electrode 1.

[0012] However, the organic EL materials 4, 6 and 8 are weak to oxygenand moisture in an atmosphere. When the organic EL materials 4, 6 and 8are exposed to the oxygen and the moisture, a macromolecule chain of theorganic EL materials 4, 6 and 8 is disconnected, or the organic ELmaterials 4, 6 and 8 are deteriorated because the organic EL materials4, 6 and 8 react chemically with the oxygen and the moisture.

[0013] As a result, the organic EL materials 4, 6 and 8 cannot emit alight of required wavelength, or a life of the organic EL materials 4, 6and 8 are rapidly reduced.

[0014] Accordingly, the organic EL materials 4, 6 and 8 should not beexposed to the oxygen and the moisture in the atmosphere when the anodeelectrode, cathode electrode and the organic EL materials 4, 6 and 8 areformed.

[0015] For this purpose, the organic EL materials 4, 6 and 8 areisolated from the oxygen and the moisture in the atmosphere by means ofa metal can 12 and a sealant 12 a. As shown in FIG. 1, a terminal part14 of the cathode electrode 10 is not sealed by means of the metal can12 and is exposed to the oxygen and the moisture in the atmosphere.

[0016] When the terminal part 14 of the cathode electrode 10 is exposedto the oxygen and the moisture in the atmosphere, an exposed portion ofthe terminal part 14 is oxidized, so that electrical characteristics ofthe cathode electrode 10 and display characteristics of the organic ELdevice are deteriorated.

DISCLOSURE OF THE INVENTION

[0017] Accordingly, the present invention has been devised to solve theforegoing problems of the conventional art, and it is a first object ofthe present invention to provide an organic EL device for reducing thedeterioration of the electrical characteristics of a terminal part of acathode electrode.

[0018] It is a second object of the present invention to provide amethod of fabricating an organic EL device for reducing thedeterioration of the electrical characteristics of a terminal part of acathode electrode.

[0019] To accomplish the first object, there is provided an organic ELdevice comprising: a power supplying part for selectively supplying apower source having a predetermined level corresponding to image data;an anode electrode for receiving the power source, the anode electrodebeing disposed on an effective display area; an organic luminescencelayer disposed on the anode electrode; a cathode electrode disposed onthe organic luminescence layer corresponding to the effective displayarea; a power transferring part connected with the cathode electrode andextended to a non-effective display area covering the effective displayarea; and an insulating part disposed on the power transfer part, theinsulating part partially exposed at a first portion to which thecathode electrode is connected and exposed at a second portion to whichan external terminal is connected.

[0020] To accomplish the second object, there is provided a method offabricating an organic EL device, comprising: forming a thin filmtransistor on an effective display area in a matrix configuration;forming a power transferring part extended from the effective displayarea to a non-effective display area covering the effective display areawhen forming the thin film transistor; forming an insulating part on thepower transferring part, the insulating part partially being exposed ata first portion of the effective display area and at a second portion ofthe non-effective display area; forming an anode electrode on an outputterminal of the thin film transistor, the anode electrode receiving thepower source having a predetermined level corresponding to image data;forming an organic luminescence layer on the anode electrode, theorganic luminescence layer emitting a light of a predeterminedwavelength; forming a cathode electrode on the organic luminescencelayer in the effective display area, the cathode electrode beingelectrically connected with the power transferring part; and forming ashielding part for sealing the effective display area.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above objects and other advantages of the present inventionwill become more apparently by describing in detail the preferredembodiments thereof with reference to the accompanying drawings, inwhich:

[0022]FIG. 1 is a schematic view showing a conventional organic ELdevice;

[0023]FIG. 2 is a circuit diagram showing an organic EL device accordingto one preferred embodiment of the present invention;

[0024]FIG. 3 is a schematic view showing a profile of the organic ELdevice according to one preferred embodiment of the present invention;

[0025]FIG. 4 is a cross-sectional view showing a thin film transistor ofthe organic EL device according to one preferred embodiment of thepresent invention;

[0026]FIG. 5 is a cross-sectional view showing a third insulating layerof the organic EL device according to one preferred embodiment of thepresent invention;

[0027]FIG. 6 is a cross-sectional view showing an anode electrode of theorganic EL device according to one preferred embodiment of the presentinvention;

[0028]FIG. 7 is a cross-sectional view showing an organic luminescencelayer of the organic EL device according to one preferred embodiment ofthe present invention;

[0029]FIG. 8 is a cross-sectional view showing a cathode electrode ofthe organic EL device according to one preferred embodiment of thepresent invention; and

[0030]FIG. 9 is a cross-sectional view showing a sealing cap of theorganic EL device according to one preferred embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0031] Hereinafter, preferred embodiments are described with referenceto the accompanying drawings.

[0032]FIG. 2 is a circuit diagram showing an organic EL device accordingto the present invention.

[0033] Referring to FIG. 2, an organic EL device 200 includes aplurality of organic EL elements 210, 220 and 230. In the presentembodiment, one organic EL element 210 among three organic EL elements210, 220 and 230 will be described.

[0034] The organic EL element 210 includes two TFTs 290 and 300, animage maintaining capacitor 240, driving signal lines 250, 260 and 270,and a pixel 280.

[0035] A first thin film transistor 290 indicates a switchingtransistor, and a second thin film transistor 300 indicates a drivingtransistor.

[0036] The driving signal line referred to as a reference numeral 250indicates a gate line connected with a gate electrode 292 of theswitching transistor 290. The driving signal line referred to as areference numeral 260 indicates a data line connected with a sourceelectrode of the switching transistor 290. The data line isperpendicular to the gate line 250. The driving signal line referred toas a reference numeral 270 indicates a bias line parallel to the dataline 260.

[0037] The switching transistor 290 is formed in an internal area thatthe gate line 250 is intersected with the data line 260.

[0038] The gate electrode 292 of the switching transistor 290 isconnected with the gate line 250, and the source electrode 294 of theswitching transistor 290 is connected with the data line 260.

[0039] The drain electrode 296 of the switching transistor 290, which isoperated as an output terminal, is connected with a first electrode 242of the image maintaining capacitor 240, and simultaneously connectedwith a gate electrode 302 of the driving transistor 300 in parallel.

[0040] A second electrode 244, which is opposite to the first electrode242 of the image maintaining capacitor 240, and a source electrode 304of the driving transistor 300 are connected with a bias line 270 towhich a predetermined power source is applied. A drain electrode 306 ofthe driving transistor 300 is connected with the pixel 280.

[0041] A predetermined power source is applied to all data line 260sequentially. The first gate line 250 receives a power source that hasenough voltage to turn on the switching transistor 290 for a shortperiod. The channel layer of the switching transistor 290 remains as aconduction state according as the power source is applied to the gateline. The power source applied to the data line 260 is output to thedrain electrode 296 of the switching transistor 290 through the sourceelectrode 294 and the channel layer (not shown) thereof.

[0042] The power source applied to the drain electrode 296 of theswitching transistor 290 is applied output through two paths.

[0043] Firstly, the power source is output to the first electrode 242 ofthe image maintaining capacitor 240. Since the second electrode 244 ofthe image maintaining capacitor 240 has already received the powersource, the image maintaining capacitor 240 is charged with electricalcharges when the first electrode 242 receives the power source.

[0044] Secondly, the power source is output to the gate electrode 302 ofthe driving transistor 300. Since the source electrode 304 of thedriving transistor 300 has already received the power source from thebias line 270, the power source applied to the source electrode 304 isoutput to the drain electrode 306 through the channel layer when thepower source is applied to the gate electrode 302 of the drivingtransistor 300. The power source output to the drain electrode 306 isapplied to the pixel 280.

[0045] The switching transistor 290 supplies the power source to thegate electrode 302 of the driving transistor 300 during applying thepower source to the gate line 250.

[0046] However, when the switching transistor 290 is turned off, theimage maintaining capacitor 240 is discharged. Accordingly, the drivingtransistor 300 turns on for a period of a frame of an image.

[0047] The power source output from the drain electrode 306 of thedriving transistor 300 is applied to the pixel 280.

[0048]FIG. 3 is a schematic view showing a profile of the organic ELdevice according to the present invention.

[0049] Referring to FIG. 3, the pixel 280 includes a transparentconductive anode electrode 282, an organic luminescence layer 283 formedon the upper surface of the anode electrode 282, a cathode electrode 284formed over the organic luminescence layer 283 with a uniform thickness,and a power transferring part 500.

[0050] Reference numerals “410” and “420” indicate an effective displayarea and a non-effective display area, respectively. The image isdisplayed through the effective display area.

[0051] The anode electrode 282, the organic luminescence layer 283 andthe cathode electrode 284 are disposed in the effective display area410. The effective display area 410 is encapsulated by means of themetal can 700 to prevent the effective display area 410 from beingdeteriorated by the oxygen or the moisture. The cathode electrode 284 isnot oxidized because the cathode electrode 284 is sealed by means of themetal can 700.

[0052] However, when the cathode electrode 284 is isolated from theoxygen or the moisture by means of the metal can 700, the power sourcefrom the non-effective area cannot be applied to the cathode electrode284.

[0053] The power source may be applied to the isolated cathode electrode284 through the power transferring part 500.

[0054] A first end of the power transferring part 500 is disposed on theeffective display area 410 and a second end opposite to the first end ofthe power transferring part 500 is disposed on the non-effective displayarea 420.

[0055] Particularly, the first end of the power transferring part 500 isconnected with the cathode electrode 284 disposed in the effectivedisplay area 410, and the second end of the power transferring part 500is connected with the external terminal (not shown) disposed in thenon-effective display area.

[0056] The power transferring part 500 is covered by means of aninsulating thin film 600 except two portions of the power transferringpart 500. A first portion of the power transferring part 500 is aportion that is connected with the external terminal, and the secondportion of the power transferring part 500 is a portion that isconnected with the cathode electrode 284.

[0057] The insulating thin film 600 reduces the oxidization of the powertransferring part 500.

[0058] FIGS. 4 to 9 are cross-sectional views showing an organic ELdevice according to the present invention.

[0059]FIG. 4 is a cross-sectional view showing a thin film transistor ofthe organic EL device according to the present invention.

[0060] Referring to FIG. 4, the switching thin film transistor and thedriving thin film transistor are formed on the substrate 281 in thematrix configuration.

[0061] In FIG. 4, the driving thin film transistor 300 is shown.

[0062] The driving thin film transistor 300 includes a channel layer301, a first insulating layer 305, a gate electrode 302, a secondinsulating layer 308, a contact hole 309, a source electrode 304 and adrain electrode 306. Processes for forming the driving thin filmtransistor 300 are the same as that of the switching thin filmtransistor, so that the switching thin film transistor has the drivingthin film transistor 300.

[0063] The driving thin film transistor 300 is formed on the substrate281 in the effective display area 410.

[0064] The channel layer 301 is formed by depositing an amorphoussilicon layer on the substrate 281 and by patterning the amorphoussilicon layer by means of a photolithography process. Amorphous silicondoped by n⁺ ions may be used instead of the amorphous silicon.

[0065] The first insulating layer 305 is formed over the substrate 281to cover the channel layer 301.

[0066] After forming a gate metal layer on the first insulating layer305, the gate metal layer is patterned to form the gate electrode 302.The gate electrode 302 is disposed on the portion, which corresponds tothe upper surface of the channel layer 301, of the first insulatinglayer 305.

[0067] The second insulating layer 308 insulates the gate electrode 302.For this purpose, the second insulating layer 308 is formed over thesubstrate 281.

[0068] The contact hole 309 is formed by partially etching the first andthe second insulating layers 305 and 308 via a photolithography process.The contact hole 309 is placed at both sides of the gate electrode 302,which is adjacent to the gate electro de 302. The channel layer 301 isexposed through the contact hole 309.

[0069] The source and the drain electrodes 304 and 306 are formed viapatterning a source/drain metal deposited on the second insulating layer308.

[0070] In the process of forming the source and the drain electrode 304and 306, the power transferring part 500 is formed, which is extendedfrom the effective display area 410 to the non-effective display area420.

[0071]FIG. 5 is a cross-sectional view showing a third insulating layerof the organic EL device according to the present invention.

[0072] Referring to FIG. 5, the third insulating layer 600 is formed onthe substrate 281 to cover the driving thin film transistor 300 and thepower transferring part 500.

[0073] The third insulating layer 600 is patterned to form contact holes610, 620 and 630, the contact hole 610 is formed on a portion of thedrain electrode 306, the contact hole 620 is formed on the effectivedisplay area of the power transferring part 500, and the contact holes630 is formed on the non-effective display areas of the powertransferring part 500.

[0074]FIG. 6 is a cross-sectional view showing an anode electrode of theorganic EL device according to the present invention.

[0075] Referring to FIG. 6, in order to form the anode electrode 282, athin film made of the ITO or the IZO is deposited on the thirdinsulating layer 600. The thin film is patterned to form the anodeelectrode 282, and the anode electrode 282 is connected with the drainelectrode 306.

[0076]FIG. 7 is a cross-sectional view showing an organic luminescencelayer of the organic EL device according to the present invention.

[0077] Referring to FIG. 7, the organic luminescence layer 283 ispartially formed on the anode electrode 282. The organic luminescencelayer 283 includes the red organic luminescence for emitting the lighthaving the red wavelength, the green organic luminescence for emittingthe light having the green wavelength or the blue organic luminescencefor emitting the light having the blue wavelength. The reference numeral“282 a” is an organic wall wrapping an edge portion of the anodeelectrode 282 as shown in FIG. 7.

[0078]FIG. 8 is a cross-sectional view showing a cathode electrode ofthe organic EL device according to the present invention.

[0079] Referring to FIG. 8, the cathode electrode 284 is formed on theupper surface of the substrate 281 under the effective display area 410to cover the organic luminescence layer 283.

[0080] The cathode electrode 284 is connected with the organicluminescence layer 283 and simultaneously connected with the contacthole 620 of the third insulating layer 600, the power transferring part500 being exposed through the contact hole 620.

[0081]FIG. 9 is a cross-sectional view showing a sealing cap of theorganic EL device according to the present invention.

[0082] Referring to FIG. 9, the sealing cap 700 is formed to seal theeffective display area 410 by means of a sealant 710.

[0083] Hereinafter, referring to FIGS. 2 and 3, the method fordisplaying the image by means of the organic EL device will bedescribed.

[0084] The data line 260 receives a predetermined power source.. Thegate line 250 receives a power source having a voltage level higher thana threshold voltage for the switching transistor 290.

[0085] Thus, the power source applied to the data line 260 is applied tothe drain electrode 296 of the switching transistor 290 through thesource electrode 294 and the channel layer of the switching transistor290.

[0086] Next, the power source applied to the drain electrode 296 of theswitching transistor 290 charges the image maintaining capacitor 240,and simultaneously applies a power source having a voltage level higherthan the threshold voltage to the gate electrode 302 of the drivingtransistor 300.

[0087] The power source having the voltage level higher than thethreshold voltage is applied to the gate line 250 for a short period.When it is stopped to apply the power source to the drain electrode 296of the switching transistor 290, electric charges charged into the imagemaintaining capacitor 240 is discharged.

[0088] Accordingly, the power source charged into the image maintainingcapacitor 240 is applied as a turn on voltage to the gate electrode 302of the driving transistor 300 during a time corresponding to a frame. Asa result, the anode electrode 282 receives a predetermined current fromthe bias line 270 while the image maintaining capacitance 540 is in adischarge state.

[0089] The power source V_(cathode) supplied from the external terminalis supplied to the effective display area 410 from the non-effectivedisplay area 420 through the power transferring part 500. TheV_(cathode) applied to effective display area 410 is applied to thecathode electrode 284.

[0090] Thus, the cathode electrode 284 supplies the electrons to theorganic luminescence layer 283, and the anode electrode 583 continuouslysupplies the holes. As a result, an energy level change, which is causedby bonding the electrons and the holes, occurs in the organicluminescence layer 283.

[0091] The light having the red wavelength, the light having the greenwavelength and the light having the blue wavelength are emitted based onproperties of the organic luminescence layer 283.

[0092] The light having the red wavelength, the light having the greenwavelength and the light having the blue wavelength are provided to theuser through the anode electrode 282 and the transparent substrate 281,thereby displaying a required image.

Industrial Applicability

[0093] As described previously, the cathode electrode is formed only onthe effective display area sealed by means of the metal can. Also, thepower source for the cathode electrode is applied through the powertransferring part extended from the effective display area to thenon-effective display area. Accordingly, it is possible to reduce theoxidation at the cathode electrode of the organic EL device, therebypreventing the electrical contact characteristics of the cathodeelectrode from being deteriorated.

[0094] This invention has been described above with reference to theaforementioned embodiments. It is evident, however, that manyalternative modifications and variations will be apparent to thosehaving skills in the art in light of the foregoing description.Accordingly, the present invention embraces all such alternativemodifications and variations as fall within the spirit and scope of theappended claims.

1. An organic electro luminescence device comprising: a power supplyingpart for selectively supplying a power source having a predeterminedlevel corresponding to image data; an anode electrode for receiving thepower source, the anode electrode being disposed on an effective displayarea; an organic luminescence layer disposed on the anode electrode; acathode electrode disposed on the organic luminescence layercorresponding to the effective display area; a power transferring partconnected with the cathode electrode and extended to a non-effectivedisplay area covering the effective display area; and an insulating partdisposed on the power transfer part, the insulating part being partiallyexposed at a first portion to which the cathode electrode is connectedand exposed at a second portion to which an external terminal isconnected.
 2. The organic electro luminescence device of claim 1,wherein the effective display area is surrounded by means of a metal canthat isolates the organic luminescence layer from oxygen and moisture.3. The organic electro luminescence device of claim 2, wherein the powertransferring part is a conductive thin film.
 4. The organic electroluminescence device of claim 2, wherein the power supplying part is athin film transistor.
 5. The organic electro luminescence device ofclaim 4, wherein the insulating part is an insulating thin film.
 6. Amethod of fabricating an organic electro luminescence device, comprisingthe steps of: forming a thin film transistor on an effective displayarea in a matrix configuration; forming a power transferring partextended from the effective display area to a non-effective display areacovering the effective display area when forming the thin filmtransistor; forming an insulating part on the power transferring part,the insulating part partially exposed at a first portion of theeffective display area and at a second portion of the non-effectivedisplay area; forming an anode electrode on an output terminal of thethin film transistor, the anode electrode receiving the power sourcehaving a predetermined level corresponding to image data; forming anorganic luminescence layer on the anode electrode, the organicluminescence layer emitting a light of a predetermined wavelength;forming a cathode electrode on the organic luminescence layer in theeffective display area, the cathode electrode electrically connectedwith the power transferring part; and forming a shielding part forsealing the effective display area.
 7. The method of claim 6, whereinthe shielding part is a metal can for isolating the organic luminescencefrom an oxygen and a moisture.
 8. The method of claim 6, wherein thepower transferring part is a conductive thin film formed when forming agate electrode and a source electrode of the thin film transistor.